A vehicle is mounted with an ECU (Electronic Control Unit) for controlling devices such as the engine and automatic transmission. An ECU is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Signals detected by various sensors such as an accelerator pedal position sensor, vehicle speed sensor, temperature sensor, voltage sensor and current sensor are processed by the ECU such that a command value towards a control subject is calculated.
If the signal processed by the ECU is in error, the vehicle cannot be controlled accurately. For the purpose of readily identifying a faulty site at a vehicle repair workshop or the like, it is required to store information identifying a faulty component in an RAM or the like in the ECU.
Japanese Patent Laying-Open No. 9-160602 (PTL 1) discloses a vehicle control system including a plurality of ECUs sharing control data. Each ECU determines whether the control data is proper or not, and storing, when an error is detected, all the control data obtained before and after the detection into a memory of the CPU.